Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane
In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic...
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ftmdpi:oai:mdpi.com:/2076-3263/12/1/36/ 2023-08-20T04:08:30+02:00 Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane Adrien Vezinet Emilie Thomassot Yan Luo Chiranjeeb Sarkar D. Graham Pearson agris 2022-01-12 application/pdf https://doi.org/10.3390/geosciences12010036 EN eng Multidisciplinary Digital Publishing Institute Geochemistry https://dx.doi.org/10.3390/geosciences12010036 https://creativecommons.org/licenses/by/4.0/ Geosciences; Volume 12; Issue 1; Pages: 36 apatite U–Pb/Sm–Nd isotopes metamorphism Archean Saglek Hf–Nd decoupling Text 2022 ftmdpi https://doi.org/10.3390/geosciences12010036 2023-08-01T03:49:15Z In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock’s history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event. Text North Atlantic MDPI Open Access Publishing Canada Geosciences 12 1 36 |
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ftmdpi |
language |
English |
topic |
apatite U–Pb/Sm–Nd isotopes metamorphism Archean Saglek Hf–Nd decoupling |
spellingShingle |
apatite U–Pb/Sm–Nd isotopes metamorphism Archean Saglek Hf–Nd decoupling Adrien Vezinet Emilie Thomassot Yan Luo Chiranjeeb Sarkar D. Graham Pearson Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane |
topic_facet |
apatite U–Pb/Sm–Nd isotopes metamorphism Archean Saglek Hf–Nd decoupling |
description |
In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock’s history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event. |
format |
Text |
author |
Adrien Vezinet Emilie Thomassot Yan Luo Chiranjeeb Sarkar D. Graham Pearson |
author_facet |
Adrien Vezinet Emilie Thomassot Yan Luo Chiranjeeb Sarkar D. Graham Pearson |
author_sort |
Adrien Vezinet |
title |
Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane |
title_short |
Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane |
title_full |
Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane |
title_fullStr |
Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane |
title_full_unstemmed |
Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane |
title_sort |
diachronous redistribution of hf and nd isotopes at the crystal scale—consequences for the isotopic evolution of a poly-metamorphic crustal terrane |
publisher |
Multidisciplinary Digital Publishing Institute |
publishDate |
2022 |
url |
https://doi.org/10.3390/geosciences12010036 |
op_coverage |
agris |
geographic |
Canada |
geographic_facet |
Canada |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Geosciences; Volume 12; Issue 1; Pages: 36 |
op_relation |
Geochemistry https://dx.doi.org/10.3390/geosciences12010036 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3390/geosciences12010036 |
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Geosciences |
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12 |
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1 |
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36 |
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1774720794176258048 |